A known conventional rheostat includes a resistance substrate, a brush, and an operation body. The resistance substrate contains a resistance part that is formed in an arc shape and that is formed by printing. The brush is fixed to the operation body to make contact with the resistance part. Then, the operation body is rotated by, for example, a user.
According to the rheostat structured as described above, the brush is moved by rotating of the operation body to alter a contact point of the brush and the resistance part. The rheostat outputs resistance value according to a rotation angle of the brush (a position of the brush).
The resistance part of the resistance substrate is formed on an insulating substrate by a screen printing method. That is, the substrate is superimposed onto a lower surface of a mask including a permeation part that is formed in an arc shape, and paste-formed resistance material is squeezed on an upper surface of the mask to form the resistance part.